Shortjaw Cisco

Coregonus zenithicus
NWT SARC Assessment
Not Applicable
NWT List of Species at Risk
Not Applicable
COSEWIC Assessment
Threatened
Federal Species at Risk Act list
No Status
NWT General Status Rank
Undetermined

The Shortjaw Cisco has a thin elliptical body that is covered with large, smooth scales. It is mainly silver in colour, with olive or tan colouring on the back and a white belly. Its small toothless mouth has a bottom jaw that is often shorter than, or even with, the upper jaw. The gill rakers (or comb-like structures on the inner surface of the bony arch supporting the gill) number between 32 and 46, which is typically less than other cisco species.

Cisco species identification is difficult because ciscoes can have different shapes and colours even within the same population. This variation has likely interacted with hybridization, local adaptation, and parallel evolution to produce a confounding assortment of forms and species of ciscoes.

Length: 340 to 420 mm (13.3 to 16.4 in)

Report Shortjaw Cisco sightings to WildlifeObs@gov.nt.ca

While best known from the Great Lakes, Shortjaw Cisco has been reported in a few deeper lakes from Ontario to the NWT. The Shortjaw Cisco has been found in Great Slave Lake and Tazin River. The Shortjaw Cisco, or a Shortjaw-like form, has also been found in Great Bear Lake.

Range map information

Shortjaw Cisco is a member of the same family as trout and salmon. Shortjaw Cisco eat shrimp, crustaceans and insects. In turn, they may be eaten by Lake Trout, Northern Pike and Burbot.

The Shortjaw Cisco inhabits deep waters, 55 to 180 m, with reports of movement into shallower waters during the spawning season. Juveniles have been found in water as shallow as 10 m. Shortjaw Cisco spawning occurs in the fall. Eggs are deposited over the lake bottom and are left to develop unattended. Lifespan is typically 10 to 13 years but individuals up to 20 years old have been found in Great Slave Lake. 

The Shortjaw Cisco, along with Lake Cisco (previously called Lake Herring), may have been two of the key colonizing species into lakes created as the glaciers retreated after the last ice age.

The Shortjaw Cisco is believed to be in decline in the Great Lakes region. Little is known about the abundance of the Shortjaw Cisco in the prairies and the Northwest Territories.

Potential threats in the Northwest Territories may include local habitat degradation, climate change and hybridization with other ciscoes. 

COSEWIC assessed Shortjaw Cisco as a Threatened species in 1987 and again in 2003. In 2006, the Governor-in-Council decided not to list the species under the federal Species at Risk Act and referred the Shortjaw Cisco back to COSEWIC for further consideration.

Area
Dehcho North Slave / Tłı̨chǫ Sahtú South Slave